A faucet, also referred to as a tap, is a valve used to control flow of fluid, usually water. There are many types of faucet designs and single-lever faucet design is amongst most commonly used. Single-lever faucets are popular because of convenience of control, ease of use by one hand and aesthetics, aside from manufacturing efficiencies when compared with many other faucet designs. Such single-lever faucets essentially have a lever which controls two basic functions:
a) Temperature of water flowing out of faucet.
b) Amount of water flowing out of faucet.
The faucet generally has two inlets—one for hot water and one for cold water. The user of single-lever faucet turns the lever sideways along a horizontal arc to change the mixture of hot water and cold water from inlets which then controls the temperature of water flowing out of the spout.
The user of single-lever faucet controls the amount of water flowing out of faucet by turning the lever angularly up or down along a vertical arc. This design of single-lever faucet is widely available in prior art.
The vertical arc motion of the lever is smooth, requiring even force along the entire vertical angular motion. Usually, user turns the lever to its largest-angle position to get maximum flow in one swift single motion of hand using momentum. However, for many purposes the amount of water needed from the faucet is often lesser than the maximum flow. For such purposes the lever has to be turned to an angle smaller than the largest-angle to get a flow of water which is lesser than maximum flow. This action of turning the lever to angle smaller than the largest-angle:                a) Requires the user to exercise more control on the hand. Exercising control on the hand adds to inconvenience and requires thought. Exercising more control over hand is not convenient as it does not use momentum of the motion of hand. Very often, user does not consciously apply thought to exercise more control of hand, especially when user has the easier option of simply using the momentum of hand to move the lever to its largest-angle position in a swift single motion.        b) Takes longer than the action of turning the lever to its largest-angle position with a swift single motion of hand.        c) Requires user to sometimes adjust the angle multiple times to obtain the right flow suitable for the purpose which further raises the tendency to use the momentum of hand to move the lever to its largest-angle position in a single motion.        d) May be difficult for very young children who lack necessary motor skills to have control over their hand.        e) May be difficult for very elderly people who may not have necessary strength in arm to have control over their hand.        
User thus has habitual preference of using swift single motion of hand to operate the faucet to raise the lever to its largest-angle position for maximum water-flow even when less water is needed for certain purposes. This habitual preference results in significant wastage of water. Further, more flow of water than necessary can also cause drops of water splashing around to make a mess on objects nearby, like clothes, documents or food, which then has to be cleaned, taking resources like time, effort and cleaning tools. There is thus a need for faucet with simple mechanism to provide less than maximum-flow of water when needed while maintaining the habitual preference of operating with swift single motion of hand.
RELEVANT PRIOR ARTU. S. Pat. #DateInventor (any one)4,819,909April 1989Hart5,082,023January 1992D'Alayer5,342,018August 1994Wu5,363,880November 1994Hsieh5,494,077February 1996Enoki5,522,429June 1996Bechte5,967,184October 1999Chang6,170,523January 2001Chang6,390,128May 2002Tung6,796,544September 2004Chen7,093,615August 2006Shane7,219,696May 2007Cattaneo7,287,707October 2007Kempf7,556,061July 2009Morita8,109,292February 2012Bolgar8,347,905January 2013Stirtz8,434,513May 2013Kacik9,103,102August 2015Prabhakar
U.S. Pat. No. 8,434,513 to Kacik in May 2013 is one type of cartridge used in conventional single-lever mixing faucets which has the problem described earlier of water wastage. This problem with conventional single-lever mixing faucets has been addressed in prior art with several different ways. U.S. Pat. No. 5,967,184 to Chang in October 1999 provides mechanism to place limits on the range of motion of the lever, which may compromise user experience and prevent more flow of water when situation deems so. Other methods have better temperature control and thus save on hot water and in turn energy, like U.S. Pat. No. 5,494,077 to Enoki in February 1996 and U.S. Pat. No. 5,363,880 to Hsieh in November 1994. These methods focus on energy saving by reducing wastage of hot water, and do not necessarily address wastage of cold water. U.S. Pat. No. 8,347,905 to Stirtz in January 2013 ensures that operation of faucet starts from cold water position, thereby by reducing wastage of hot water and thus energy. This method saves hot water/energy only in the initial phase of operation of faucet when appropriate temperature is being set, but not during continued usage of the faucet. U.S. Pat. No. 5,082,023 to D'Alayer in January 1992 provides a step between no-flow and maximum-flow position of the lever which the user can just push through if needed. In this mechanism there is tendency on part of user to simply use momentum of hand to operate at maximum flow step, skipping the intermediate step. More granular mechanism is offered in U.S. Pat. No. 9,103,102 to Prabhakar in August 2016, where user can increase the flow in multiple steps. U.S. Pat. No. 6,796,544 to Chen in September 2004 also takes the multi-step approach in a different way. Both latter prior art have complex mechanisms. Methods which use multiple steps approach save hot and cold water, and work during continued usage of faucet. However, these methods rely on user to change their way of operating a faucet. User behavior is habitual and thus difficult to change, especially in inconsequential matter of operating a faucet. Users continue to prefer the single swift motion of hand to operate the faucet.
There is thus a need for faucet which makes it convenient to reduce water usage while allowing user to continue to use their habitual preferred method of operation.